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use super::plumbing::*;
use super::*;
use std::fmt::{self, Debug};
/// `FlatMapIter` maps each element to a serial iterator, then flattens these iterators together.
/// This struct is created by the [`flat_map_iter()`] method on [`ParallelIterator`]
///
/// [`flat_map_iter()`]: trait.ParallelIterator.html#method.flat_map_iter
/// [`ParallelIterator`]: trait.ParallelIterator.html
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[derive(Clone)]
pub struct FlatMapIter<I: ParallelIterator, F> {
base: I,
map_op: F,
}
impl<I: ParallelIterator + Debug, F> Debug for FlatMapIter<I, F> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("FlatMapIter")
.field("base", &self.base)
.finish()
}
}
impl<I: ParallelIterator, F> FlatMapIter<I, F> {
/// Creates a new `FlatMapIter` iterator.
pub(super) fn new(base: I, map_op: F) -> Self {
FlatMapIter { base, map_op }
}
}
impl<I, F, SI> ParallelIterator for FlatMapIter<I, F>
where
I: ParallelIterator,
F: Fn(I::Item) -> SI + Sync + Send,
SI: IntoIterator,
SI::Item: Send,
{
type Item = SI::Item;
fn drive_unindexed<C>(self, consumer: C) -> C::Result
where
C: UnindexedConsumer<Self::Item>,
{
let consumer = FlatMapIterConsumer::new(consumer, &self.map_op);
self.base.drive_unindexed(consumer)
}
}
/// ////////////////////////////////////////////////////////////////////////
/// Consumer implementation
struct FlatMapIterConsumer<'f, C, F> {
base: C,
map_op: &'f F,
}
impl<'f, C, F> FlatMapIterConsumer<'f, C, F> {
fn new(base: C, map_op: &'f F) -> Self {
FlatMapIterConsumer { base, map_op }
}
}
impl<'f, T, U, C, F> Consumer<T> for FlatMapIterConsumer<'f, C, F>
where
C: UnindexedConsumer<U::Item>,
F: Fn(T) -> U + Sync,
U: IntoIterator,
{
type Folder = FlatMapIterFolder<'f, C::Folder, F>;
type Reducer = C::Reducer;
type Result = C::Result;
fn split_at(self, index: usize) -> (Self, Self, C::Reducer) {
let (left, right, reducer) = self.base.split_at(index);
(
FlatMapIterConsumer::new(left, self.map_op),
FlatMapIterConsumer::new(right, self.map_op),
reducer,
)
}
fn into_folder(self) -> Self::Folder {
FlatMapIterFolder {
base: self.base.into_folder(),
map_op: self.map_op,
}
}
fn full(&self) -> bool {
self.base.full()
}
}
impl<'f, T, U, C, F> UnindexedConsumer<T> for FlatMapIterConsumer<'f, C, F>
where
C: UnindexedConsumer<U::Item>,
F: Fn(T) -> U + Sync,
U: IntoIterator,
{
fn split_off_left(&self) -> Self {
FlatMapIterConsumer::new(self.base.split_off_left(), self.map_op)
}
fn to_reducer(&self) -> Self::Reducer {
self.base.to_reducer()
}
}
struct FlatMapIterFolder<'f, C, F> {
base: C,
map_op: &'f F,
}
impl<'f, T, U, C, F> Folder<T> for FlatMapIterFolder<'f, C, F>
where
C: Folder<U::Item>,
F: Fn(T) -> U,
U: IntoIterator,
{
type Result = C::Result;
fn consume(self, item: T) -> Self {
let map_op = self.map_op;
let base = self.base.consume_iter(map_op(item));
FlatMapIterFolder { base, map_op }
}
fn consume_iter<I>(self, iter: I) -> Self
where
I: IntoIterator<Item = T>,
{
let map_op = self.map_op;
let iter = iter.into_iter().flat_map(map_op);
let base = self.base.consume_iter(iter);
FlatMapIterFolder { base, map_op }
}
fn complete(self) -> Self::Result {
self.base.complete()
}
fn full(&self) -> bool {
self.base.full()
}
}